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Abstract

Despite the status Rubus armeniacus (Himalayan blackberry) has as one of the most prolific and damaging plant invaders in the Pacific Northwest, we know little about the role of water relations in its success. The information available on invasive blackberry water relations (Fotelli et al. 2001; McDowell and Turner 2002) suggests that an ability to avoid water stress has been critically important to their proliferation in regions with Mediterranean climates (Amor et al. 1998). We had two objectives regarding the role of water relations in the invasive success of R. armeniacus:

Objective 1. Determine if R. armeniacus is better adapted to the Pacific Northwest’s water regime than congeneric natives. To address this objective we tested three hypotheses: a) R. armeniacus remains less water stressed than native congeners throughout the growing season; b) R. armeniacus maintains a higher stomatal conductance at all levels of evaporative demand; and c) R. armeniacus has lower hydraulic resistance than congeneric natives throughout the growing season, as a consequence of lower root and shoot resistances.

Objective 2. Determine if and how the water relations of R. armeniacus help it to outgrow native Pacific Northwest competitors.

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This is a Center for Invasive Plant Management Research Grant Final Report awarded in 2006.